What happens to your focus when you don’t eat enough healthy fats, according to nutrition experts

For years, fat has been framed as something to cut back on, but nutritional science has made one thing clear: healthy fats are essential, especially for your brain. When you consistently eat less fat, the effects aren’t always dramatic at first, but eventually you’ll feel more sluggish and tired.

We asked nutrition and mental health experts to explain how a steady supply of healthy fats supports brain health and what to expect when consumption is reduced. Here’s how much fat you really need and what to eat to get it.

Why fat is so important for your brain

In general, healthy fats help protect brain cells and keep them flexible. “Omega-3 fats are especially important for mood and cognitive function,” says brain health researcher and author Mark Milstein. Age proof brain. “Eating enough healthy fats can also help reduce inflammation, which plays a role in long-term brain health.

In particular, fat provides functional support for the brain and metabolic support for healthy digestion. “Healthy fats promote membrane fluidity, which affects neurotransmitter signaling,” says Christy Del Coro, MS, RDN, LDN, registered dietitian and nutritionist. “Dietary fat also slows gastric emptying and improves blood sugar stability.” Fat works throughout the digestive system to help keep your energy levels steady. When your energy goes down, so does your mood and concentration.

Fats don’t just affect how your brain and stomach function—they’re actually part of the brain’s physical structure. “Adequate fat intake is essential for the brain’s structural integrity and communication systems,” says Timothy Frey, DMS(c), MS, CNE, a nutritional neuroscientist and neurobehavioral nutritionist. “Fatty acids form the lipid bilayer of nerve membranes and regulate signaling pathways that affect mood, memory, cognition, emotional processing, and really everything that happens in our brain.” In simple terms, the fat you eat helps build brain cells and supports the signals they send to each other.

What happens to your brain when you don’t eat enough fat

Over time, eating too little fat can affect how well your brain works during the day. “When dietary fat intake is too low, the brain lacks key lipid substrates needed to maintain neuron structure and function,” Frey explains. “The human brain is about 60% fat by dry weight, and fatty acids are the basic components of nerve membranes, synapses, and myelin.”

Frie points to research showing that low intake of essential fatty acids is associated with poorer cognitive function and a greater risk of neurological and psychiatric conditions such as depression and anxiety. In practical terms, a low-fat diet can cause slow thinking, difficulty concentrating, and mental fatigue during daily tasks.

Fat is also essential for the absorption of fat-soluble vitamins (A, D, E, K), which are vital nutrients for your brain health and overall mood. “Vitamin D deficiency has been linked to depression and cognitive decline, so ensuring adequate intake and proper absorption is critical for brain health,” Del Coro says. “Vitamin E also plays an important neuroprotective role as an antioxidant. A very low-fat diet puts people at risk of disrupting hormone production and affecting nutrient absorption.”

Consequences of a high fat diet

There’s a caveat, though: It’s best to eat the right kind and amount of fat because too much of the wrong kind can have negative health effects. “Unfortunately, many people consume a high-fat diet that is dominated by saturated fat,” says Frey. “These foods increase neuroinflammation, weaken insulin signaling in the brain, and weaken the blood-brain barrier. When this barrier becomes compromised, inflammatory molecules more easily enter the brain. Over time, this increases the risk of poor memory, poor cognitive function, and neurodegenerative diseases.”

How much fat do you consume per day?

Your brain and body need some fat to function. “Very low-fat diets (less than 20% of daily calories) are generally not recommended unless medically indicated,” Del Coro says. All the experts we spoke with agreed that most adults do best when about 20-35% of their daily calories come from fat. This translates to approximately 44-78 grams of fat per day on a standard 2,000-calorie diet, “although individual needs vary based on energy expenditure, health status, activity level, and life stage,” Frey says.

Among these fats, regular consumption of omega-3 fatty acids is especially important for the brain. “Most international nutrition and cardiovascular guidelines recommend about 250-500 milligrams of EPA and DHA combined per day for general health in adults,” Frey explains. For context, you can achieve this goal by eating oily fish two or three times a week. You can also get ALA omega-3s from plant sources such as chia, safflower, and walnuts.

“The key is to choose quality. Think salmon, olive oil, nuts and seeds. It’s not about eating too much fat, it’s about eating the right kind,” says Dr. Milstein. Dale Corr agrees that the quality of the oil is important. “Limit saturated fat to less than 10% of total calories to reduce your risk of heart disease,” she says, emphasizing unsaturated fats like nutrient-dense avocados.